New Zealand will maintain 27 military personnel in Afghanistan after the April withdrawal from Bamiyan, Prime Minister John Key said.

Cabinet today agreed to the deployment, which John Key said would be "behind the wire", including three SAS personnel. It would run for a year but be reassessed later this year.

Key said the situation in Afghanistan was "changeable and unpredictable".

Foreign Affairs Minister Murray McCully and Defence Minister Jonathan Coleman said it was a small but proportionate military commitment to the international mission in Afghanistan from May 2013.

"The current NATO/ISAF mission is not scheduled to end until December 2014. As previously indicated, the Government believes it remains in New Zealand's interests to continue to play our part to secure the gains that have been achieved in Afghanistan over the last decade," McCully said.

"Most of these deployments will, initially, operate from the closing of the PRT in April, for a one-year period to the end of April 2014."

Coleman said the 27 NZDF personnel would be based in Afghanistan, predominately in the capital, Kabul.

The group will comprise:

Eight NZDF personnel deployed to the UK-led Afghan National Army Officer Training Academy in Kabul from later this year. As announced last year, this particular deployment is likely to extend beyond 2014

Three NZDF support personnel as part of the New Zealand "National Support Element "

One NZDF officer with the UN Assistance Mission to Afghanistan

Colman will this week visit Brussels for the NATO/ISAF Defence Ministers' Meeting where he will set out 'These deployments are in addition to our commitment announced last year to contribute US$2 million per year from 2015 to help sustain the Afghan National Security Forces after the ISAF mission concludes."

New Zealand would also continue with development assistance to Bamiyan province after the withdrawal of the Provincial Reconstruction Team.

The New Zealand Embassy in Kabul is expected to close before the end of 2014